Human Anatomy at Colby

Ivan Yang: My experience in A&P

February 24th, 2015 · Comments Off on Ivan Yang: My experience in A&P

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Even though I am a molecular biology major, I had not taken any biology courses in the fall semester, so my advisor highly recommended me to take a biology course for JanPlan. After checking the course listings for January, I decided on a whim to sign up for the Intro to Human Anatomy and Physiology course. Later that week, I met someone who had taken the course last January. She informed me that if I was to take BI265, I would have to be prepared to learn a lot in a small amount of time. There was a wealth of interesting knowledge to be gained from the course, but, she warned, if I was expecting to cruise through JanPlan, I should drop the course. Not sure if I should take her seriously or not, I laughed it off and didn’t think about her words much after that.

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After the first week, I definitely knew that this class was not to be taken lightly. The first week was especially rough because of the flipped lecture setting. Not only did we have to study for daily quizzes and lab exams, but also we had to listen to lecture and lab podcasts for the following day’s lecture and lab sessions. I was completely unprepared, and I was forced to adjust my mentality, my study schedule, and my lifestyle habits. However, while there was a seemingly surreal amount of work involved in the course, the amount of material that I absorbed during the four weeks of JanPlan truly astounded me. In addition, after putting in maximal effort just to learn the basics of human anatomy and physiology, I gained deep respect and admiration for the structure and workings of the human body. I truly came to enjoy the class and the subject, and soon enough I found myself embracing Dr. K’s recommended healthy lifestyle habits.

Beyond learning material through lectures and labs and finding a healthy lifestyle balance between working and resting, I also had many opportunities to do things that I had never done before. For example, for the first time in my life, I had the opportunity to perform a wet dissection of a pig heart. Although I was confused at first due to initial difficulties in matching the neatly-drawn heart schematics in my mind with the real deal in my hands, I thoroughly enjoyed the experience of opening the heart with my own hands, placing my fingers through the valves and blood vessels to see where they connected, and seeing how the real tissues and membranes of the heart correlated with the models in our anatomy lab. In fact, I’m sure I would have enjoyed the experience even more if my partner and I had remembered that there were scalpels available for use in the dissection (we had to cut through a very thick ventricular wall with a very small pair of scissors – if you are taking the class and haven’t done the wet dissection yet, REMEMBER that there are scalpels available for use).

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In sum, BI265 was a welcome and intellectually stimulating challenge. I absorbed a great deal of anatomy and physiology in the last four weeks, worked with wonderful classmates and a great professor, and learned about myself, my study and lifestyle habits, and stress management. I would recommend this class to anyone interested in thinking and in challenging his/her intellectual limits.

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The blood vessel model – my best friend during the weekend before the second lab test.

 

Tags: Bi265j

Ivan Yang: Musings on the Fetus vs. Mother Battle

February 23rd, 2015 · Comments Off on Ivan Yang: Musings on the Fetus vs. Mother Battle

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One of the best yet most challenging parts of this course is the sheer volume of knowledge that can be gained in these four weeks. I learned a spectacular amount of information about the human body during the course, giving me a greater appreciation for the ingenuity of evolution and the delicate intricacy of the body’s structures and mechanisms. In addition, Dr. K has a knack for sprinkling little bits of knowledge throughout his lectures that, when given time to soak in, can stimulate a great deal of critical thinking.

For example, when Dr. K lectured on the respiratory system, he briefly mentioned that fetal hemoglobin has higher oxygen saturation than adult hemoglobin does at the same oxygen levels. While this assertion can be explained by the fact that the fetus has higher demand for oxygen and must compete for oxygen in slightly deoxygenated blood, it reminded me of an article I read in a previous biology class on imprinted genes.

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Imprinted genes are genes which are “marked” by the maternal or paternal parent and which are expressed over other versions of the same gene. Mechanisms of imprinted gene expression and evolutionary reasons for their existence are mostly obscure due to their relatively recent discovery. In fact, the existence of imprinted genes was only verified through cloning experiments in the late 80s. Scientists attempting to create a uniparental mouse (a mouse with two paternal or two maternal sets of DNA) found that it was impossible to create a fully-developed uniparental embryo. When the embryo was created from two maternal sets of DNA, its cells were properly organized, but the placenta was insufficient. When the embryo was created from two paternal sets of DNA, it was able to form a very healthy placenta, but the fetus itself was a disorganized mass of cells.

These results flew in the face of Mendelian genetics, which suggested that genes are merely strands of information with no history of origin. To the contrary, genes do, in a sense, remember their parental origins. The studies in the 80s suggested that the expression of certain genes in the paternal genome is responsible for making the placenta, while the expression of certain genes in the maternal genome is responsible for organizing the embryo. One of the first explanations posited that the placenta should be thought of not as a maternal organ designed to support the fetus, but rather as a fetal organ designed to parasitize the mother. While the mother and the fetus both have the common purpose of perpetuating the continued survival of the fetus, they disagree over how much of the mother’s resources should be dedicated to the fetus. In a sense, maternal genes are “selfish” and only the genes necessary to organize the fetus are expressed. Hence, the uniparental mouse embryos made of two maternal sets of DNA were unable to create a sufficient placenta.

This competition for resources between the fetus and the mother, clearly observable through research on imprinted genes, is strikingly similar to the competition for oxygen between the fetus and the mother. As previously mentioned, fetal hemoglobin has a higher oxygen affinity than adult hemoglobin does. To ensure its own survival, it is entirely conceivable that the fetus robs oxygen from the mother’s bloodstream. Perhaps this is but another example of a battle of wills between the fetus and the mother.

 

Tags: Human Health

Grand Rounds: CABG v. PCI Stenting

January 28th, 2015 · Comments Off on Grand Rounds: CABG v. PCI Stenting

CABG vs. Stenting in Multi-vessel Procedures: A Synopsis

Mayra Arroyo, Chris Lee, Ivan Yang

Coronary artery disease is caused by atherosclerosis, or the accumulation of fatty deposits, known as plaque, along the innermost layer of the coronary arteries. There are three main coronary arteries: the right coronary artery, circumflex artery, and the left anterior descending artery.  Atherosclerosis causes the afflicted coronary artery’s wall to thicken and lose elasticity, ultimately narrowing or blocking the artery. This can reduce the oxygen flow to the myocardium. Treatment of coronary artery disease is complex and depends on several factors, but typically comprises of risk factor management, medication, and interventional techniques, such as coronary artery bypass grafting (CABG) and stenting.

Percutaneous Coronary Intervention (PCI) or Stenting is a minimally invasive process in which a doctor inflates a stent (mesh steel tube) with a balloon to open up a clogged artery. This restores normal blood flow. A catheter is inserted through the groin, neck, or arm to move the stent to the affected area.  In recent years, newer types of stents such as drug-eluting stents and biodegradable ones have been developed. Before choosing stenting as a treatment option, one should consider risks involved with stenting such as damage to the vessels or arteries.

CABG is a surgical procedure where a vein or artery (usually from the inner thigh) is used to form a path around a blocked coronary artery. Over the years, there have been changes to the techniques used to carry out CABG. One such example is Totally Endoscopic CABG, which uses a robot equipped with a camera and surgical instruments in its arms. It is important to note that this procedure is highly invasive and risky, which is why it is usually used after more conservative treatments have been attempted.

In the three studies discussed, we compared long-term outcomes of CABG and stenting in multi-vessel disease in diabetics and in combined subgroups by looking at death rates, adverse event rates, and repeat revascularization rates.  Multi-vessel disease is defined as the occlusion of two or more of the three main coronary arteries, and revascularization is a procedure that returns blood flow to a low-oxygen area.

In diabetics, we found that CABG ultimately has better long-term outcomes in multi-vessel treatment.  Primary outcome (death, heart attack, or stroke) rates and all-cause mortality rates were lower in CABG diabetic patients than in diabetic patients who underwent drug-eluting stent procedures.

A study published in 2001 observed the effects that CABG and stent had on patients one year after treatment. The patients’ quality of life (survival and freedom from stroke, heart attack, or repeat revascularization) was examined after one year. It was found that there were no significant differences between the number of CABG and stent patients who did not die or have heart attacks or strokes. However, CABG patients had lower rates of repeat revascularizations than stent patients. In light of this study, it is important to remember that it was conducted in a time before drug-eluting stents and other newer treatment options.

Another study published in January of 2013 found that, compared to CABG patients, a greater percentage of people who underwent PCI with drug-eluting stents underwent repeat revascularization. The study concluded that in people with less complex disease, it is acceptable to undergo PCI. On the other hand, people with multi-vessel problems should choose CABG.

In conclusion, though CABG has proven to have better long-term outcomes than stenting in multi-vessel disease treatment, better studies should be conducted to verify this.   Future studies should include more patients, cover modern CABG and stent techniques, and be extended for several years after revascularization.  For now, it appears that CABG does have an advantage over stenting and drug-eluting stents, mostly due to reduced rates of repeat revascularization.

 

Tags: Grand Rounds